The invention relates to a device for applying a flowable medium, in particular a single- or multiple-component tissue adhesive.
A number of embodiments of application devices for flowable media (pasty or liquid media) are known (EP-B 0 037 393, EP-B-0 210 160, U.S. Pat. No. 4,874,368, U.S. Pat. No. 4,978,336, DE-A-42 23 356, EP-B-0 315 222, WO-A-96/19940, WO-A95/31137 and WO-A-98/40167). According to the application it is sometimes necessary and desirable to dosedly discharge the medium. In the case of application devices for medical tissue adhesives it is particularly desirable that the doses are reproducible and relatively small. This discharged quantity should further be independent of the duration of manual operation of the application device.
For hygienic reasons it is further advantageous when the application devices are designed as non-returnable and/or disposable articles. This, in turn, requires the mechanisms for medium discharge in a dosed manner and independent of the application device to be of relatively simple configuration. If, besides the medium, a gas is to be discharged, by means of which the discharged medium can be sprayed onto an article, it is appropriate to control the dosing mechanism for the medium with the aid of the pressurized gas. Such an application device for technical media is known from EP-A-0 548 509. However, said known application device is not suited for use with nonreturnable and/or disposable articles due to its rather complex structure.
It is an object of the invention to provide an application device for flowable media, the application device displaying a simple structure suitable for configuration of the application device as non-returnable and/or disposable article.
According to the invention, the object is solved with an application device provided with
at least one reservoir for the medium, the reservoir comprising an outlet from which the medium exits when pressure is applied to the medium and/or the reservoir,
a pressure-generating element for applying pressure to the medium and/or the reservoir,
a biasing means for biasing the pressure-generating element, the biasing means comprising a movable biasing element which is pneumatically and/or hydraulically biased towards the pressure-generating element and coupled with the latter,
a controllable locking means for locking the biasing element, the locking means comprising a movable fixing element which, in at least in one fixing position, locks the biasing element against movements caused by the biasing process and is movable out of the at least one fixing position to release said biasing element, and
a release means for selectedly releasing the locking means, the release means comprising a release element for temporarily moving the fixing element of its at least one fixing position.
Further aspects of the invention are stated in the subclaims.
The flowable medium to be discharged by the device according to the invention is located in a reservoir which comprises an outlet. If the medium is a multiple-component medium, the components of which are to mixed with each other only during the discharge process, a separate reservoir is provided for each component. The medium is hydraulically discharged from the reservoir by pressure application. The pressure acting upon the medium is applied by a pressure-generating element. Said pressure-generating element acts either upon the medium in the reservoir or from outside upon the reservoir which, in this case, must be of flexible configuration. In the first case, in particular a syringe is used as a reservoir, with the piston of the syringe and the piston rod serving as the pressure-generating element.
In the device according to the invention the pressure-generating element used for discharging the medium is biased. This is realized by biasing the pressure-generating element towards the reservoir with the aid of a biasing means. Said biasing means operates pneumatically and/or hydraulically, with in particular the pressure of a gas, which may be used for atomizing the discharged medium, being applied. The biasing means comprises a biasing element coupled with the pressure-generating element. Said biasing element is biased towards the pressure-generating element. The freedom of movement of the biasing element is limited by a locking means. In its normal position said locking means blocks the movement of the biasing element towards the pressure-generating means. With the aid of a release means locking of the biasing element can be released selectively and for a predeterminable period of time. Said release means comprises a release element which temporarily sets a fixing element, which locks the biasing element, into a position in which said fixing element releases the biasing element.
The biasing means appropriately comprises a medical syringe to the outlet nozzle of which a hose coupled with a compressed-gas source is connected. The piston rod end and the flanges and/or wings of the barrel of the syringe are supported between a fixed point and the biasing element. By application of pressure the piston and the piston rod are pushed out of the barrel and/or biased towards the outside. This pressure is utilized to move the biasing element towards the pressure-application element acting upon the medium reservoir.
The locking device is appropriately configured in the form of teeth meshing with each other. For this purpose the biasing means and in particular the biasing element is provided with at least one toothed rack cooperating with a fixing projection of the fixing element. If said fixing projection is in engagement with said toothed rack, movement of the biasing element is blocked. By moving the fixing element such that the fixing device is disengaged from the toothed rack the biasing means and/or the biasing element is released so that it moves in forward direction following the biasing force. Release of the biasing means and/or the biasing element is controlled by the release element which, on its part, moves the fixing element.
The toothing, i.e. the succession of teeth of the toothed rack, determines the measure by which the biasing element can move forward when it is released. If it is requested that extremely small fluid quantities are discharged, the toothed rack must display a correspondingly fine toothing. However a fine toothing is of disadvantage in so far as the meshing of the fixing projection with the toothed rack requires a high degree of finishing accuracy. This finishing accuracy is realizable only in plastic injection molded parts with higher efforts being made, which plastic injection molded parts are to be preferably employed in the device according to the invention. The reason for this is that the device according to the invention is to be configured as non-returnable and/or disposable article. Therefore it is advantageous to use toothed racks with a rougher toothing. To be able to discharge small dosing quantities even with such a tooting, it is advantageous to provide two toothed racks instead of one toothed rack at the biasing means and/or the biasing element, said toothed racks being staggered, in particular by a fraction of the distance between the teeth, preferably half the tooth distance. Consequently, the fixing element comprises two fixing projections. Said fixing projections as well as the toothed racks are arranged at opposite sides and/or sides averting each other of the fixing element and/or the biasing element. By reciprocating the fixing element a respective one of the fixing projections alternately meshes with one of the toothed racks. Even in the intermediate states of movement of the fixing element the biasing element is not released such that the desired step-by-step advance movement is limited exclusively by the alternate meshing of the fixing projections with the toothed rack and the staggered toothed rack arrangement. The fixing element is in both fixing positions protected against unintentional movements in that due to the bias a clamping force is exerted via the respective toothed rack on the fixing element. This force suffices to retain the fixing element in engagement with the respective toothed rack.
If only one toothed rack is used, mechanical biasing of the fixing element appropriately ensures that said fixing element automatically moves back into the locking position (the fixing projection meshes with the toothed rack) after release of the biasing element. The release element then operates against this biasing force in that it moves the fixing element of the locking device against the biasing force.
As has already been stated above, a mechanical coupling exists between the pneumatically and/or hydraulically biased biasing element and the pressure-generating element acting upon the fluid and/or the reservoir for the purpose of discharging the medium. The biasing element can, on the one hand, be directly coupled and/or connected with the pressure-generating element. Alternatively, coupling can be realized by employing an intermediate or connecting element. Said connecting element is appropriately configured as an actuating element for manually moving the pressure-generating element. Said actuating element is supported on the biasing element and can be manually moved relatively to said biasing element and protected against unintentional displacement. The actuating element can advantageously be configured as a spindle in threaded engagement with the biasing element. One end of said spindle is connected via a rotatably supported receiving element and/or a rotatably supported connecting element with the pressure-generating element, whereas the other end comprises a handwheel or a similar handle by means of which the spindle can be rotated. This configuration allows the pressure-generating element to be manually moved alternatively to the biasing element. This offers the advantage that the device according to the invention can optionally be used for manually discharging a medium quantity which is no longer limited in terms of volume. In the case of this application the pressure-generating element is then moved away from the biasing element by operating the spindle. If the reservoir is configured as a syringe, this spindle can also be used for taking in, via the syringe outlet, medium to be discharged from the syringe. The pressure-generating element is moved towards the biasing element by operating the spindle, whereby a vacuum is produced in the barrel of the syringe due to which vacuum the medium to be discharged (later) is taken into the barrel of the syringe.
The device according to the invention is preferably accommodated in a pistol-shaped housing, which is appropriate for the purpose of application of the medium and thus for handling purposes. Such a housing comprises a handle at which appropriately a finger-operated actuating element in the form of a pushbutton, lever or the like is arranged. For reasons of space it is further advantageous when in such a housing the reservoir containing the medium is horizontally arranged. This, in turn, means that the pressure-generating element is horizontally arranged either, i.e. moves in parallel to the movement of the actuating element. Since the pressure-generating element is coupled with the biasing element, the biasing force, too, ensures that the biasing element is movable in parallel to the actuating element. This movement of the biasing element is to be effectively blocked and/or selectively released by the fixing element when said fixing element is movable transversely to the biasing element to, on the one hand, block the biasing element and, on the other hand, release the biasing element. In the final analysis, this means that the movement of the actuating element, which releases the biasing element, must be deflected essentially by 90xc2x0 to move the fixing element in transverse direction. This movement deflection means is appropriately provided with a swivelling element swivelling about a swivelling axis extending transversely to the directions of movement of the release element and the fixing element. Said swivelling element is coupled with the fixing element and comprises a swivelling arm upon which acts the release element. When the release element presses against the swivelling arm, the swivelling element is swivelled about the swivelling axis. Due to the coupling of the swivelling element with the fixing element a linear movement of the fixing element goes along with this swivelling movement. Such an arrangement is suitable for moving the fixing element from a fixing position into a release position. The fixing element is appropriately moved back from the release position into the fixing position with the aid of a biasing force mechanically applied to said fixing element.
If a structure with a fixing element alternately movable between two fixing positions is selected as locking and release mechanism, the swivelling element of the movement deflection means comprises two swivelling arms arranged opposite each other, with the release element alternately acting onto these swivelling arms. Owing to that the swivelling element is alternately pivoted in different directions, which results in a movement of the fixing element from the one fixing position into the other fixing position. In this structure the swivelling element has the form of a xe2x80x9cTxe2x80x9d whose horizontal legs form the two swivelling arms and whose vertical leg is coupled with the fixing element, wherein the swivelling axis is located in the point of intersection of the two legs.
As has already be said above, it is sometimes desirable to atomize the medium discharged with the aid of a device according to the invention. This requires synchronous discharge of a gas, wherein the gas should continue to be discharged for a certain time interval after termination of the medium discharge to prevent medium droplets from forming at the outlet of the device. For this purpose a valve controlling the gas discharge is preferably used, the valve being controlled by the pressure of the gas the discharge of which is to be influenced by the valve. While it is desirable that the passage state of the gas discharge valve is assumed as erratically as possible, change-over of the valve from the passage state to the blocking state is to be effected in a delayed manner. This is appropriately realized by employment of a xe2x80x9cdifferentialxe2x80x9d gas discharge valve whose housing comprises two interconnected chambers with different diameters and/or cross-sectional areas. In the two chambers a piston is arranged. In particular at opposite ends of the two chambers gas inlet openings are arranged to which the pressurized gas-carrying lines are connected. In the chamber with the smaller cross-section a gas outlet is located, while the chamber with the larger cross-section contains a vent hole to be opened when required. In the normal state said vent hole is closed by a closing element.
In the blocking state of the valve the vent hole is closed. Since the associated chamber (hereinafter referred to as first chamber) has a larger cross-section than the other chamber (hereinafter referred to as second chamber) and the gas pressure is identical in both chambers, a larger force acts upon the front face of the piston located in the first chamber than upon the front face of the piston located in the second chamber. Consequently, the piston is displaced towards the second chamber until it bears upon a limit stop defined by a shoulder-shaped tapered area of the housing. In this piston position the piston seals the gas outlet of the second chamber.
By opening the vent hole the pressure in the first chamber is abruptly reduced. In the second chamber the overall gas pressure still prevails. Consequently, the piston moves into the first chamber whereby the gas outlet of the second chamber is cleared. Now the gas at the gas inlet of the first chamber is fed via the gas outlet of the first chamber; the valve is in its passage position.
As soon as the vent hole is closed again, the pressure in the first chamber rises again, namely to the value of the pressure in the second chamber. Due to the larger piston front area in the first chamber the piston moves again towards the second chamber until, in its final position, it closes the gas outlet. The velocity at which this process takes place depends, on the one hand, on the ratio of the front face sizes of the piston, and, on the other hand, on the rate at which the gas flows into the first chamber. This rate can be limited and adjusted by a flow restrictor or a similar flow rate-determining element such that the valve displays the desired time switching characteristic.